January 26, 2009

Expose-R installed on the outside of the ISS

After leaving Earth on November 26, 2008, the Expose-R instrument of ESA carrying nine experiments was set up outside the Russian module of the ISS on March 10. The objective of the mission is to analyse the effect of space environment on biological objects and molecules which are of interest to exobiology and/or planetology.
Michel Viso Responsable du Programme Exobiologie au CNES (crédit photo : Michel Viso)
Michel Viso, Exobiology Program Scientist at CNES - credit: Michel Viso

“Expose-R is the fourth experimental rack built by ESA to be dedicated to exobiology” says Michel Viso, Exobiology program scientist at CNES. It follows in the footsteps of the EURECA-ERA (1992-1993) and Biopan (1993,1997,1999) experiments and comes to complete the Expose-E payload.

In the beginning, the Expose project came following a call for proposals of ESA and the payload was meant to be attached to the European module Columbus. Given the delays between the conception of Expose and the launch of Columbus, ESA decided to negotiate with Russia in order to set up an equivalent payload on the Russian module Zvezda. “Ironically, Expose-E (E for Europe) reached the ISS a few months before Expose-R (R for Russia), which was set up in February 2008”, says Michel Viso smiling.  The two instruments have the same capacity to host samples but ESA chose different experiments.

EXPOSE-R lors de son installation (crédit photo : ESA)
View of Expose-R as it was being set up with Earth in the background - credit: ESA

Expose-R is equipped with three sample-holding trays each containing four sample carriers (77 x 77 x 26 mm). Each tray hosts four sample carriers on which are mounted the cells containing the samples. Some cells are airtight and sealed with windows, others are left open to the open space. Each tray is loaded with sampled of organic molecules and biological samples made of plant seeds, spores, bacteria, mould and ferns. The samples are exposed to UV radiation, space vacuum and extreme temperature variations during a year and a half.

The nine experiments carried by Expose-R:
AMINOHervé Cottin (F)Effects of light radiation on amino acids and other organic compounds in Earth orbit
 ENDOCharles Cockell (UK)Effects of space environment on endolithic microorganisms (living in rocks)
 OSMORocco Mancinelli (I)Exposition of osmophile microorganisms (living in sugar-rich environment) to space environment
 SPORESGerda Horneck (D)Spores placed in artificial meteorites
 PHOTOJean Cadet (F)Effects of solar radiation on the genes of spores
 SUBTILNobuo Munakata (Japon)Mutation effects of space environment on bacteria spores (Bacillus subtilis)
 PURGyörgyi Ronto (Hun)Effect of space environment on the T7 phage, its DNA and polycrystalline uracil
 ORGANICPascale Ehrenfreund (NL)Evolution of organic matter placed in space
 IMBPVladimir Sychev (Russie)Exposition of terrestrial organisms in dormant state

Some of the Expose experiments study how particular terrestrial organisms survive and cope with extraterrestrial environment conditions. The goal is to measure the survival rate of biological samples and the biological effect of radiation to validate planetary protection measures and test some hypotheses of the panspermia theory. Other experiments, such as Amino, test how organic molecules react when they are submitted without filter to solar radiation during a long period of time.

Shedding light on Amino

Hervé Cottin LISA (crédit photo : Françoise Fritche)
Hervé Cottin LISA - credit: Françoise Fritche

The objective of the Amino experiment is to better understand the nature and evolution of organic matter in extraterrestrial environments and their potential implications in exobiology. Numerous ground experimental programs study the photochemistry of molecules in solid state and gaseous state. “Nonetheless, the validity of these experiments and applying them to extraterrestrial environments can be questioned as long as they have not been confronted to similar experiments in space, which involves exposition to the full solar spectrum, especially in the short wavelengths spectrum, something that isn’t easily simulated in laboratories”, explains Hervé Cottin, Lecturer at Université Paris 12 from LISA and Principal Investigator of the Amino experiment.

Amino’s basic principle is to expose molecules in solid or gaseous state to solar radiation. These molecules are handpicked for the benefits they can bring to the study of either comets, meteorites, or organic chemistry on Titan. They Include polyoxymethylene, hexamethylenetetramine, HCN and C3O2 polymers, either pure or in organic or mineral matrix for comets; amino acids for meteorites; tholins and N2/CH4 gaseous mixes for Titan. Some are dedicated to the study of organic chemistry in Mars environment, such as glycine, hopanoids, lipids, kerogens and benzoic acids. “We’re trying to better understand the chemical processes which occur on the surface or in the atmosphere of different Solar System objects such as comets, meteorites, Mars or Titan” adds Hervé Cottin. The effect of solar radiation on RNA-based molecules is also studied.

The Amino experiment was supported by CNES and prepared by LISA (cometary chemistry and chemistry in the atmosphere of Titan and on Mars), LATMOS (Titan and Mars), the Center for Cellular and Molecular Biology of Orléans, France (for meteorites), the Jacques Monod (radiation impact of NRA) and INRA (radiation impact on seeds).

At the end of the exposure period, EXPOSE E will be bought back on the ground by the Space shuttle in August 2009. In 2011, the sample-holding trays of Expose-R will be brought back to Earth by a Soyuz module and transferred to the Microgravity User Support Center (MUSC) in Cologne (Germany). From there, the samples will be distributed to scientists for analysis.

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